Hi I know the head of water is determined by the height of the water level above the ground ie 10 metres high gives 1 bar pressure at ground level - but is that head altered by the amount of water in the storage tank? For instance will a 50 gallon tank of water gives 2 bar of pressure if sited at 10 metres above ground.

Water head pressure is static pressure caused by the weight of water solely due to its height above the measuring point. The pressure at the bottom of a 40-foot lake or a 40-foot high thin tube would be identical, since only height is involved.

I just got this from the internet. It explained the point better than I could